It really depends. My dude and I have been together for a decade - that's not something that can be thrown away lightly. If it led to some serious conversations about our expectations and what each of us are/are not getting out of our relationship, I think it could still work.
On the other hand, if he was having an emotional relationship with another woman - I would FLIP. I'm not a jealous person, but I know I'm emotionally high-maintenance.